Limitations of the SEASAT SAR in High Sea States

Abstract

Although the spectral analysis of SEASAT SAR imagery has shown qualitatively good agreement with independent surface spectral measurements, quantitative two-dimensional ocean energy spectra from SAR imagery remain an elusive goal. The exact relationship between the ocean wave energy spectrum and the corresponding SAR image spectrum constitutes the central problem of much recent research. This chapter outlines a systematic approach to estimation of ocean wave spectra from SAR image spectra based on recent analysis of SEASAT SAR digital data. The effect of the various wave-imaging mechanisms, the stationary scatterer resolution response function, and the moving scatterer resolution response function are considered. Corrections for the latter two effects are applied to actual SAR image spectra. Particular attention is paid to the degradation of the azimuth component of SAR spectra in moderate to high sea states by the moving scatterers, which limit the ability of the SAR to image azimuthtraveling waves. This effect is quantitatively modeled and predictions of the model are shown to agree with actual SAR spectra. Corrections for the moving scatterer resolution response function are shown to result in better estimation of the position of remote storm sources.